Phase Behavior of Doxycycline Hyclate-Incorporated Bleached Shellac In Situ Forming Gel/Microparticle after Solvent Movement

With regard to the periodontal pocket application of in situ forming systems, the understanding the phase behavior after solidification owing to solvent movement could verify the deformability of specimen and its capacity to reside in the artificial periodontal pocket. The aim of this research was to investigate the phase behavior by determining mechanical properties as hardness and elasticity/plasticity ratio with texture analyzer for matrices obtained from drug-free and doxycycline hyclate (DX)-incorporated bleached shellac (BS) in situ forming gel (isg) and –microparticle (ism) after solvent exchange. The solvents for dissolving BS were 2-pyrrolidone (PYR), N-methyl pyrrolidone (NMP) and dimethyl sulfoxide (DMSO). The matrix from isg was less rough and bulge than that of isg. The order of mechanical hardness of transformed system prepared with different solvents was presented as PYR > NMP > DMSO, influenced by phase separation rate and porosity. The systems prepared with NMP and DMSO were more likely plastic or able to adapt its geometry to dynamic changes while that prepared with PYR was elastic. DX-incorporated ism matrix was still governed by the oil in external phase; thus, its consequence was reasonably plastic instead. XRD pattern indicated that the solvent type had no effect on the crystallinity of remained BS after solvent movement. SEM topography revealed sponge-like structure of isg prepared with DMSO and NMP whereas that prepared with PYR exhibited only initiated diminutive pores. The size and density of pores increased by time of isg using different solvents as following DMSO > NMP > PYR, whereas ism matrices had less pore density. The level of porosity of each matrix reflected the mechanical strength that a higher porous structure collapsed easily but a dense matrix considerably resisted to a compression.